The WAVES model has been used by CSIRO in its sustainable yields Projects (Crosbie et al. 2008) and the Bureau built on this methodology. WAVES was run for all combinations of soil, vegetation and depth to water table at each climate point. A groundwater discharge value was estimated for each 1 km × 1 km pixel across the region using annual rainfall, dominant soil and vegetation, and depth to water table. This discharge value can be positive or negative, due to evapotranspiration. Discharge within the Melbourne region was determined by summing the pixels with a positive estimate (red areas).

WAVES model dicharge areas

Assumptions, limitations, caveats and approximations

Assumptions made when developing the WAVES model (Dawes et al. 1998) are all applicable to the discharge estimations carried out for the Melbourne region.

The Bureau of Rural Sciences' land use map of the Melbourne region was reclassified to three vegetation classes – annuals, perennials and trees. The major vegetation classes modelled are C3 annual pasture, C3 perennial pasture and eucalypt trees with a grassy understorey.

Discharge was estimated to be within the clipped sedimentary area, considering the effects of shallow water tables.

Diffuse discharge to groundwater from irrigation applied to the landscape is not included in the estimate.

Uncertainty information

The uncertainty in the input parameters and the corresponding impacts on the modelled discharge values have not been studied.

The uncertainty of the estimated discharge resulting from different discharge interpolation methods was not estimated.